Dual voltage, series-parallel switches are available in various forms for connecting windings of a transformer into either a series or parallel connection. Each winding in the transformer is generally made up of three coil segments. The leads to each coil segment being connected to the fixed contacts on the dual voltage switch block. A rotor, having two bridge contacts, is provided within the switch block to selectively connect the fixed contacts in either a series or parallel relation. One switch assembly is generally provided for each phase and additional switch assemblies connected to the first switch assembly for each additional phase in the transformer. In addition, back-deck assemblies can also be provided to include different fuses and/or auxiliary tap coil segments into the series-parallel circuits as required by the transformer rating.
Dual voltage switches presently available are generally complex, including specially formed pinch contacts to join with the leads for the coil segments, expensive insert molded machined studs and bridging contact subassemblies which are movable to various positions to interconnect the contact leads. Where multiple phase units are required, the switches are stacked together with spacers glued to the switches to hold them together. In some instances molded spacers are used with threaded fasteners to provide a mechanical connection. Where individual phase decks are used, they have been mounted on an outside frame. Interconnection of the rotors has resulted in inconsistent connections between the rotor contacts and switch contacts because of the different type of switches used to provide the various switch functions.